Exposure to traumatic events is a common experience for children and adolescents. Accurate early assessment of acute stress responses can help predict risk for longer term sequelae and can guide secondary prevention to reduce the incidence and severity of PTSD after trauma exposure. However, there is no established self-report measure of ASD for children and youth. The goal of the proposed research is to develop a practical self-report measure of Acute Stress Disorder (ASD) for children and adolescents, and to provide initial evidence as to its reliability and validity. The specific aims of this application are: Aim 1: Establish the content validity of a pilot Child ASD measure for ages 8 to 17, based on expert review and youth feedback. Aim 2: In a sample of recently injured children, assess the psychometric properties of the measure: internal consistency, test-retest reliability, convergent and discriminant validity with other measures and other reporters. Aim 3: Provide initial data regarding the predictive validity of the Child ASD measure in relation to later PTSD development in the same sample of children. The proposed project will build on preliminary work done by Dr. Kassam-Adams and collaborators in developing and refining a reliable and valid measure of child Acute Stress Disorder, practical for use in the acute post-trauma period. After refining and revising a measure of child ASD with expert review and youth feedback, the project will assess the test-retest reliability of the new measure over 2 to 7 days. The project will also assess the measure's association with: (1) concurrent assessment of the same symptoms by parent and by a clinician, (2) concurrent child self-report on a measure of closely related symptoms, (3) concurrent measures of related or divergent child symptoms, and (4) child report of later PTSD outcome. In its aim to create a valid child ASD measure for practical application in acute care settings, the proposed project advances the NIH research objective to" increase the number of persons seen in primary health care who receive mental health screening and assessment. The proposed project also fulfills the NIMH priority category 1 for Small Grants to newer, less experienced investigators. The Principal Investigator is a newer investigator who is developing a program of research into child and parent post-traumatic stress in relation to injuries and medical emergencies.